Eva Carneiro was dropped from first-team duties on 8 August after she and physio John Fearn were criticised by José Mourinho for going on to the pitch to treat Eden Hazard. Photograph: Mike Egerton/PA

Lawyers acting for the former Chelsea team doctor Eva Carneiro have served notice on the club that she intends to bring a claim for constructive dismissal, having failed as yet to agree a severance package following her departure last month.

Legal papers are understood to have been served on the Premier League champions earlier this week as time in the three-month window permitted for claimants to lodge any complaint ticked down towards its deadline of 8 November. The papers will trigger an employment tribunal unless an out-of-court settlement can be agreed before a hearing takes place. Such tribunals are conducted in public and could be embarrassing for either defendant or claimant, meaning a compromise is usually struck beforehand.

José Mourinho clear to be in Chelsea dugout for critical Liverpool match

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Carneiro and the club’s physio Jon Fearn were publicly criticised by Chelsea’s manager, José Mourinho, for legitimately entering the field of play to treat Eden Hazard in stoppage time at the end of the 2-2 draw with Swansea City on 8 August. The referee, Michael Oliver, had waved the medical staff on to the pitch, with the Belgium international apparently in need of treatment – the medics were obliged to comply – although that meant the hosts played out a period of added time with only nine men on the field after the earlier dismissal of Thibaut Courtois.

The doctor and physio were subsequently dropped from first-team duties. Chelsea have consistently refused to comment publicly on what they consider to be an internal staffing matter but, whereas Fearn remains at the club, Carneiro did not report for work in the period after the incident and formally left last month, with her legal team entering negotiations to stave off any legal action. Mourinho has since been cleared by the Football Association of using discriminatory language towards Carneiro on the touchline, although the doctor released a statement criticising the governing body over its investigation of the incident.

“I was surprised to learn that the FA was allegedly investigating the incident of 8 August via the press,” she said this month. “I was at no stage requested by the FA to make a statement. I wonder whether this might be the only formal investigation in this country where the evidence of the individuals involved in the incident was not considered relevant. Choosing to ignore some of the evidence will surely influence the outcome of the findings.”

Although there is still scope for compromise to be reached, the ramifications of the fallout have added to the sense of chaos at Chelsea over what has been a traumatic season. Mourinho and his team go into Saturday’s potentially pivotal game against Liverpool 15th in the Premier League table after five defeats in 10 matches and with two disciplinary issues hanging over the manager. The Portuguese and his assistant Silvino Louro will be in the dugout at Stamford Bridge, despite being sent to the stands at West Ham last Saturday, with their misconduct charges to be heard by a commission next week at the earliest.

The Chelsea manager is also appealing against a £50,000 fine and suspended one-match stadium ban for suggesting officials were “afraid” to award his side decisions following the defeat by Southampton on 3 October. That appeal over the scale of the punishment was initially expected to be heard this week.

The champions’ Brazil midfielder Ramires signed a new contract through to 2019 on Thursday, in effect serving as a two-year extension, although even that was overshadowed by news that his compatriot Lucas Piazon, a young forward on a season-long loan at Reading, is wanted by police in Toronto in connection with an alleged sexual assault.

A warrant has been issued for the arrest of Piazon and his Brazil Under-22s team-mate Andrey da Silva Ventura after an alleged incident during the Pan-Am Games last summer. Police allege a 21-year-old woman was sexually assaulted by two men who met her at a downtown club on 25 July and then went to her home. It is alleged the woman was sexually assaulted after she fell asleep and the two men fled the scene.

The alleged incident occurred on the same day Brazil won the bronze medal in the tournament, with Piazon, who moved to Chelsea for £5m in 2011 from São Paulo, scoring in a 3-1 win over Panama. Both Chelsea and Reading, for whom Piazon scored at Fulham on Saturday, confirmed they were “aware of the reports” but made no further comment. The forward is understood to have trained as normal with Steve Clarke’s squad on Thursday.